1. The Field of the Invention
The present invention relates to the manufacture of semiconductor devices. More particularly, the present invention is directed to methods for providing improved bottom and side wall coverage of high aspect ratio features in the manufacture of a semiconductor device.
2. The Relevant Technology
The ever increasing circuit density of state of the art semiconductor devices has resulted in increasing aspect ratios for various structures formed during the manufacture of integrated circuits. Particularly for such structures as contacts and vias, higher aspect ratios have had a negative effect on fabrication yields. Aspect ratio, defined herein as the height of a feature with respect to the width thereof, is considered to be a high if it is at least 2 to 1. Adequate bottom coverage of high aspect ratio contacts and vias has been somewhat difficult to achieve. To provide a deposition system capable of depositing a film with adequate bottom coverage of high aspect ratio features, collimated sputtering is typically employed. But when deposition is performed in a collimated sputtering system with sufficient collimation to provide adequate bottom coverage of high aspect ratio features, then the side walls of high aspect ratio features can be left without adequate coverage. Decreasing the collimation, by, for example, decreasing the collimator aspect ratio, can result in pinching off of the high aspect ratio space before adequate bottom coverage can occur. Thus a method of providing adequate coverage both of side walls and of bottom surfaces of high aspect ratio features is needed.